This work is concerned with the ontogeny of rat ingestive behavior. Specifically, it assesses: 1. The environmental controls of suckling. This will be evaluated by manipulating the characteristics (e.g., touch, temperature, etc.) of surrogate mothers, 2. How suckling comes under the control of reinforcement. This will be assessed by permitting rats, raised from birth on an intragastric tube, to suckle a nonnutritive surrogate mother and to then deliver various substances intragastrically, e.g., water, milk, or LiCl. The point during ontogeny at which these postingestinal manipulations affect later suckling will be assessed as will the critical delay between oral and postingestinal events, 3. Development of feeding in infant rats. This will be assessed by permitting rats, raised on the intragastric tube, daily access to arrays of edible-nutritive, edible-nonnutritive and nonedible objects. The development of preference for the edible-nutritive objects will be determined as will the critical interval between ingestive and postingestive events necessary for reinforcement to be established, 4. The effects, on adult behavior, of raising newborn rats, in isolation, on an intragastric tube. The regulatory and motivational capacities of weaning, adolescent and adult rats, raised from birth on the intragastric device, will be determined by a variety of nutritional and hydrational challenges. This will help evaluate the effects of the suckling experience on later motivated behavior, 5. The effects of temporary anosmia, produced by intranasal injections of zinc sulfate, on suckling behavior and on later adult ingestive behavior. We have already discovered that this maneuver in 4-day old rats leads to a permanent reduction in adult body weight. We will seek the basis of this phenomenon by determining food and water intake and body weights of rats made temporarily anosmic during various stages of ontogeny. The effects of this treatment on suckling and on adult motivated behaviors will also be evaluated.